I want this action, in a 357 mag or 44 mag. Be a lot better of a gun than the Ruger's I think

I'm sorry. Laughs at you in French, Dutch, AND German waffles.

On a serious note, I like the P90 up till you have to reload the magazines. I always hated the loading those.

The P90 is just blowback right? I think it is but can't remember

Yup, straight blowback, and generally regarded as the most controllable SMG ever made. The mags take about the same time to change out as any other SMG of that era. If it were made today, they would probably integrate some kind of strong side mag release. You could reengineer it so the mag popped out the front or something I guess. Speed reloads don't happen that often in the real world though. If you run dry and don't have plenty of time to reload, you're going for your sidearm. They only take marginally longer to reload than anything else though, and they have almost double the capacity so you're a lot less likely to run dry in the first place.

I will say, it is pretty controllable, but I think that has to the layout of the gun as well as it's cartridge.

I meant loading the magazines with ammo, not the reloading the gun. To me the P90 magazines just took a little longer to load than the UMP and the MP5 we had on the line.

Don't the mags also have a tendency to jumble the ammo when dropped partially-loaded, badly enough that they need to be disassembled to fix it? I seem to recall that was an issue during the NATO PDW trials way back when.

A shame the Germans wouldn't adopt the superior 5.7 cartridge. I think the MP7 was the better gun for the PDW role, while the P-90 is more a legit carbine by size and weight.

Like actually putting the bullets in the mag? Idk to me they’re super easy to load. You just have to do it 20 more times than with a normal smg.

The mp7 is actually bigger and heavier than it looks, plus the capacity is much lower. One of the big selling points for the p90 is the slim profile with nothing sticking out. You can really sling it and forget it. The mp7 you have that big banana sticking out the bottom.

it's well over a pound lighter, and can be holstered (albeit not exactly the slimmest holster setup). With a 20 round mag in the gun, and 40's in pouches, it gives up little to the P-90.

The P-90 is more controllable, though, no doubt. But it is also the same weight as a compact AR and more than a M1 carbine.

Yea, I just remember it being time consuming to me.

I'd be pretty interested to shoot one of CMMG's 5.7 pistols and compare it to the p90. I'd like to think it would be an even better shooter.

Yea, they take all day to load and 1.5 seconds to empty. But boy those 1.5 seconds sure are fun.

Tell me about it. Tried the FN PS90 a couple times at the range. Takes a bit of a time to load them all (50 round mag) but doesn’t take more than a few winks to empty the whole mag :((

Basically like feeding 20s into an industrial paper shredder.

wow, thats great man!

haha thats adorable how the dogs toes are in the pic rather than yours

maybe theory is that the place for gas to be diverted to reduced the pressure pussing the casehead agains the breech as a way to slow the action??  I would think that a dead end expansion chamber would quickly become clogged w/ carbon tho?

A lot of words were used in this thread to say "stop liking what I don't like".

Don't forget that most people buying a 9mm carbine don't want to spend over $500 for what they consider a plinker. If it takes Glock mags that's a plus since they already have a pile of Glock mags.

Who cares if the recoil is a little snappier and it doesn't suppress as well. It's still fun to take the range and plink.

Of course there are better systems, but they cost a lot more and not worth it to most buyers. I'm not spending over $1k on a plinker.

happened into this thread when someone suggeted the stribog

heard that they are getting approvals for a delaysed blowback version, the A3.  Here is a guy shooing standard blowback and delayed, full auto

https://www.youtube.com/watch?v=XoN4viUWiXI

I responded to you on that here: https://www.ar15.com/forums/ar-15/9mm-PCC-advise/15-744206/?r=-1&page=1&anc=7979078#i7979078

Ugh, "Striborg" fail.  My last boss did that all the time to the name, too

I do notice the lighter-recoiling A3 also has a big honkin' brake on the muzzle (the difference in ROF is the real tell that the system is doing something, though; about 1/4 the recoil is being soaked up by the barrel/bolt if the ROF drops from 800rpm to 600rpm)

Brakes on 8” 9mm do almost nothing. I have one on my USPSA PCC and it’s pretty much just for show.

They can have an effect up to 40% reduction on a handgun with 4” barrel and a much lighter gun.

The whole point of this thread wasn’t the “I don’t like blowback”. It’s that when you understand what delayed does - you can’t go back.

I bet the A3 is much better than the A1. I don’t know if it’s the same as MP5 or CMMG RDB, but that depends on just how delayed it is. 600RPM should be great, but i have doubts the blowback A1 is 800rpm, because an MP5 is 850rpm.

If you haven't before, pick up an MP5 bolt carrier group sometime; they feel like they're made of Styrofoam, compared to the OG G3.  Stupid light, like a locked breech system would be.

The main thing I'd figure the big comp would do is add a lot of weight out front, which definitely does have an effect; for that reason alone you treat it as apples-apples --but that wasn't the point, obviously, showing off a cool gun was.  If all it does is reduce the RPM by 25% through dissipating breach thrust to the receiver, that's still plenty more than useful.

A discussion about the flaws of straight blowback is sort of a first world problem.

...and we live in the first world.

Blowback sucks.

Shoot a blowback and a delayed gun back to back and you realize how much better the delayed is. Yes, even in semi-auto. Just how it is. If all you have ever shot is blowback then you don't know what you don't know. You owe it to yourself to shoot a delayed 9mm.

Delayed systems are nice and all from a technical point of view but recoil on 9mm PCC is so ridiculous that the extra cost & extra parts of a delayed system is not worth IMHO..

This reminds me of the rotating barrel system on some handguns.. is it nice? Sure.. but looks more like a solution looking for a problem..

Ever shot a standard AR9 before? It recoils more than it should. Recoils more than a 5.56 AR. Massive BCG on the AR9 riding back and forth. Competition AR9 overcome this with fancy parts (read expensive) and massive muzzle brakes.

Look at the cost of a JP GMR-15 9mm compared to the price of a CMMG RDB. There really isn't a extra cost and extra parts.

this

I own a Scorpion but have shoot a few different 9mm PCC including the mp5 and a AR PCC conversion..
The AR has never been a ideal PCC platform.. the delayed system fixed it sure but every other blowback PCC is plenty controllable.

Have to say, I find shooting my direct blowback Scorpion less fun than my Zenith Z-5RS, CMMG Guard, and even my .45 cal LWRC SMG-45.

Hmm.  My Colt 9mm shorty, with a AAC Ti-Rant 9s sounds and recoils about the same as 22, with subs in it you think you had a squib load or such the first time you fire it, and check to see if things are OK.

For full auto fire I can see the difference, but for semi work, blowback is fine.  I bough the 9mm buffer from Spikes, made just for the 9mm rifle, and haven't had any bolt catch breakage issues.

9mm Tavor shoots as soft as any PCC I’ve fired.  I believe it is straight blowback.

Yup. PCC’s are dumb unless they’re a SMG. I’m not investing thousands into a semi auto 9mm. I went with a Ruger PC Carbine because I have a bunch of Glock mags already. If I didn’t then I would have maybe bought a Scorpion or Stribog...but even that is at the top of the price range. And no...I won’t go be poor somewhere else...I just spend my money on far more capable firearms within the limitations of the NFA. I’ve had an HK94, PS-90, Vector Uzi, and now the Ruger. Honestly, the Ruger is more fun than any of those were. The ghost ring sights and a G19 mag make it feel and handle like a cheap to shoot M1 carbine. It scratches that itch for me. If I want an effective PDW then it’s going to be an 8” .300 BLK.

I’ve found that too, but with one caveat.  I’m comparing my Tavor to my other PCC pistols/SBRs with 8” or shorter barrels, which are a bit lighter.  The extra weight of a 16” barrel carbine soaks up some of the recoil.

No more so than a rotating bolt on an autoloading rifle is a solution looking for a problem, when SKSs/FALs worked just dandy

But the discussion in the context of mandatory semi-auto sure isn't.  Friggin' NFA...

I like that people who don’t know what the delayed action difference is are arguing “it has more parts!!”... the CMMG RDB has less parts than a DI AR, and we all know those are unreliable!

I’m glad to see more people realizing most AR9s have more recoil than their 556 counterparts. Needlessly.

This whole thread is have and have nots of noticing the difference.

That’s an apple to orange comparison..

A delayed SMG usually has more parts and machining than a Blowback one.. that’s why they cost more.

I’m not saying delayed smg are crap.. innovation and options are always a good thing. I’m just saying that this thread title is meh.. a first world problem..

i'll go be poor somewhere else, straight blowback has worked perfectly for me

It really doesn’t matter much for a range toy.

Ian from Forgotten Weapons lays down pretty well why straight blowback is so prevalent (and just fine)

go to 1:12:51

Unnecessary complexity, extra bolt weight not that big a deal.

Why try to move forward, when we can stay where we are?

Straight blowback is not just fine if you want the best design you can, have the best performance you can and the best gun you can have. It is just fine if you want mediocre and just good enough. The reason it is so prevalent has already been said; it is cheap to design and manufacture and the general public (1) doesn't know better because they haven't shot a variety of guns or (2) the public (and even governments) want the cheapest they can afford and hence you get straight blowback.

Extra bolt weight is a big deal. Leads to more recoil. Leads to less accuracy as you have a massive heavy bolt moving back and forward. Compare a blowback to a delayed gun and keeping your sight picture while rapid firing. There is a big difference in performance.

Best is relative here and "SIMPLE, "INEXPENSIVE" are relevant design characteristics, from military to police to civilian consumers.  blowback gives you much fewer parts and a much simpler receiver design (versus rollers in a bolt as well as the corresponding roller 'accepting' surfaces in the receiver walls or trunnion or if talking gas, then you need a gas vent hole, size it right, a piston and bolt carrier).  So the tradeoff for that added expense and complexity had better result in real substantial tangible benefit.  In the gun world, for better or worse, you get a lot of inertia (why worry about fixing what mostly already works just fine).

looking at the competition world.  PCC shooters are still a lot of straight blowback AR shooters.  If using gas/rollers was a "game changer" those guys would be using them universally (kind of like how quad loading has taken over 3gun shotgun).  and even then, its a specific application where fractions of a second are paramount and they are much more aware of maintaining their weapons (and have the funds to afford the most expensive stuff).  The average joe and the military customer on the other hand...

One may argue, "well look at the mp5, best PCC ever", it exploded in popularity in the mil/police world and its stuck around, undeniably a great design.  Consider at the time of its popularity/adoption its primary competitors were clunky open bolt blowbacks, versus closed bolt roller delayed.  now THAT is an example of a "game changing" substantial difference in performance worth the added cost/complexity of an mp5 vs an UZI.  The mp5 sticks around even amongst arguably better guns (in terms of ergos, mounting optics, etc) in large part because of inertia, again... "well we have the mp5, its competitors are only marginally better at best, why waste the time and money switching".

I agree that "SIMPLE" and "INEXPENSIVE" are also relevant design characteristics. But I disagree with your premise and argument that only straight blowback offer you "SIMPLE" and "INEXPENSIVE."  But instead of focusing on just the higher end delayed options like the Kriss Vector or HK MP5 as your delayed guns, you need to expand to the CMMG Banshee radial delayed which is similar to the price of a straight blowback gun. Or even consider the roller delayed Stribog once/if that eventually comes to the USA and is expected to be a sub $1000 gun. You can still have "SIMPLE" and "INEXPENSIVE" if you look.

Just because competition shooters typically use straight blowback ARs doesn't mean that is the best route. They typically use straight blowback ARs because of the AR familiarity and what it offers them in regards to triggers and ergonomics. They also include all kinds of fancy muzzle brakes and recoil buffers. Nothing "SIMPLE" or "INEXPENSIVE" there, right? You ever look up the price of a JP GMR-15 9mm or other guns typically used in PCC events? That won't classify as "INEXPENSIVE." Quite the opposite.



If you want to talk competition world, that is completely different and not how I understood @new21022 intention of this thread. Wasn't geared towards competition PCC shooting. But then again, you are getting in the "NOT INEXPENSIVE" territory. I see mention a lot of guys on this forum that do participate in PCC events and have been running the CMMG RDB quite well. Why run a straight blowback gun with a heavy bolt when you can run a lighter gun with less recoil with the same ergonomic and trigger benefit of the AR platform?

Ooops, beat on the mention of the JP GMR-15.

I have owned a few 9mm ARs in the past and currently own a blow back 4.5" 9mm built on a glock mag NFA/Joebobs lower.

When CMMG RDB bolts/barrels became available, I spent too much money and built a second 9mm AR that was the shorter RDB barrel option.

I didn't see enough difference in the RDB action to warrant the cost difference. It was also finicky with my lighter loaded reloads.

Maybe part of me not seeing much difference is because I shoot soft shooting 124 grain powder coated cast lead rounds. Haven't chronied them, but they are around 1050FPS subs.

I sold the CMMG parts and went back to my shitty blowback;)......it seems more reliable.

I do still have and love my 5.7 Guard. That's a keeper!

Added.....I do not shoot suppressed.

@Mad-Machinist
Please tell us more...

What makes your configuration special/different?

Does yours have less felt recoil than CMMG's RDB?
The pricing is similar.

When throwing reloads into the mix that changes a lot.  As I've mentioned before, I had high hopes for the CMMG RDB when I got it and while I could certainly tell a difference comparing to a straight blowback 9mm AR/M16, I felt it lagged behind the MP5 but I knew it had potential so I continued on the tweaking.

I'm wondering if your reloads would even run in an MP5.  IMHO, I think that is the standard to which all closed bolt SMG's need to strive to meet or exceed in terms of the recoil impulse.
For Open bolt, there are several 9mm SMG's that are MP5 smooth and some arguably smoother.
I've emailed Rudy (Mad-Machinist) about his post.  I told him I agree to disagree with him on that.  He thinks locked breech is the only way to go...doesn't seem to be a fan of delayed mechanisms.   As I've posted before, over a decade ago, the smoothest I got my 9mm M16 to run was with a ported barrel using an LRM integrally suppressed upper, no bolt weight and the old Olympic Pneumatic buffer which required a rifle length buffer tube.   That buffer ended up leaking and was worthless after a few matches.

Even so, the more you try to smooth out a 9mm M16, the more the cyclic rate goes up.  I know many probably don't care about that but I do.  Being straight blowback they also won't suppress as well....which I care about and obviously some people don't.

IMHO, having less recoil in a 9mm SMG than an M4 is not that impressive....again having less recoil than an MP5 is impressive.

Don't know if any of you have seen this thread: https://www.ar15.com/forums/AR-15/DPM-Recoil-Reduction-System-vs-Hydraulic-buffer-EDIT-Armament-LARB-Mod-2-and-3-added-to-the-test-/118-744494/?page=1

We are actively working on testing an accelerometer to give quantitative data to go along with subjective data in terms of recoil.  I am also doing high speed video (1000 frames per second) of a cut out buffer tube to watch the buffer and spring.

In the videos you can see how much the gun kicks and the forward momentum of the gun from the BCG/buffer/spring going forward.  I've got some ideas to lessen that....



Here is a MK18 with the standard 'milspec' configuration - .070" gas port, H2 buffer, standard spring (white sprinco).


Now here is the 9mm CMMG with the CMMG recommended buffer/spring configuration.  Firing was done from a lead sled, strangely, it would run 100% from the shoulder but would jam in the sled....
Again better than straight blowback but not MP5 smooth.


Now my preferred configuration with my modified 5.45 bolt to optimize the delay for suppressed usage....since this bolt was optimized for 147gr suppressed usage, it doesn't lock back on the last round when a suppressor is not mounted and runng 115gr.
At the time, I forgot to put my 300BLK Tubb spring in there.  It will lock back with that spring UNsuppressed....I'll do a vid of that next time.


I added the suppressor in this video.


You can see that there is very little rearward recoil impulse.  I think this is MP5 smooth....
I'm going to do a high speed video of the same buttstock area firing the MP5 with the same ammo for comparison.
I am also going to do a few more videos with a straight blowback 9mm M16 w/ the standard Colt bolt weight, SAW tungsten bolt weight as well as some hydraulic buffers and the 9mm JP SCS.
I'm sure all of the straight blowback videos will clearly show more recoil than these videos.

However, as you can see in the other thread, I was hoping we could get the accelerometer dialed in so I could get data from that as well as do the high speed video at the same time as this is very time consuming to do all this.

Mantis also sent me their X10 to test for muzzle rise as well so will hopefully get data from that also.

I will admit to being FAR from a SME on the subject.  But I can tell you that I have a Scorpion and recently built a gun using CMMG barrel and bolt RDB system with their mag guts.  Less than 100 rounds through it, but it has functioned 100% without having to tune buffer system (H buffer is in there I believe?), both on semi and full auto, suppressed and no suppressor. I'm impressed thus far.  It is smooth, accurate, and not gassy suppressor.